Java 8 compiler bug?

[Jonathan Gibbons]

Thanks for the reduced test case.

-- Jon

On 11/15/2016 04:32 PM, Oliver Gierke wrote:
> I wasn't sure whether any specialty of the types involved is causing the issue, that's why I kept the JPA dependency in the first place. But this piece of code shows the same characteristics:
>
> public class Ambiguity {
>
> 	public void foo(CriteriaBuilder builder) {
>
> 		Expression<Object> objectExpression = null;
> 		Expression<Collection<Object>> collectionOfObjectExpression = null;
> 		builder.isNotMember(objectExpression, collectionOfObjectExpression);
> 	}
>
> 	interface Expression<T> {}
>
> 	interface CriteriaBuilder {
>
> 		<E, C extends Collection<E>> void isNotMember(E elem, Expression<C> collection);
>
> 		<E, C extends Collection<E>> void isNotMember(Expression<E> elem, Expression<C> collection);
> 	}
> }
>
>> Am 16.11.2016 um 00:54 schrieb Jonathan Gibbons <jonathan.gibbons at oracle.com>:
>>
>> Can you simplify your example down to something that doesn't require us to download a zip file?
>>
>> -- Jon
>>
>> On 11/15/2016 03:49 PM, Oliver Gierke wrote:
>>> Sorry, I forgot the link to the reproducing example:
>>>
>>> https://dl.dropboxusercontent.com/u/25310722/compiler-ambiguity.zip
>>>
>>>> Anfang der weitergeleiteten Nachricht:
>>>>
>>>> Von: Oliver Gierke <ogierke at pivotal.io>
>>>> Betreff: Java 8 compiler bug?
>>>> Datum: 16. November 2016 um 00:46:02 MEZ
>>>> An: compiler-dev at openjdk.java.net
>>>>
>>>> Hi all,
>>>>
>>>> I just ran in this code compiling fine with a JDK 8 if I define a compilation source and target of 1.6, but not if I define both values of 1.8.
>>>>
>>>> public class Ambiguity {
>>>>
>>>> 	public void foo(CriteriaBuilder builder) {
>>>>
>>>> 		Expression<Object> objectExpression = null;
>>>> 		Expression<Collection<Object>> collectionOfObjectExpression = null;
>>>> 		builder.isNotMember(objectExpression, collectionOfObjectExpression);
>>>> 		//      ^^^^^^^^^^^ - ambiguous
>>>> 	}
>>>> }
>>>>
>>>> CriteriaBuilder and all other types come from JPA. The method in question has two overloads:
>>>>
>>>> <E, C extends Collection<E>> Predicate isNotMember(Expression<E> elem, Expression<C> collection);
>>>> <E, C extends Collection<E>> Predicate isNotMember(E elem, Expression<C> collection);
>>>>
>>>> I fail to understand why the second method is even considered as that create a contradiction between the bound values of E (Expression<…>) and C (Collection<Object>).
>>>>
>>>> I've prepared an example here [0]. Steps to reproduce:
>>>>
>>>> 1. Unzip
>>>> 2. Run mvn clean compile -> fails
>>>> 3. Change java.version property in pom.xml to 1.6
>>>> 4. Run mvn clean compile -> succeeds
>>>>
>>>> $ java -version
>>>> java version "1.8.0_112"
>>>> Java(TM) SE Runtime Environment (build 1.8.0_112-b16)
>>>> Java HotSpot(TM) 64-Bit Server VM (build 25.112-b16, mixed mode)
>>>>
>>>> Is that a known issue, something I oversee or should I create a ticket for that?
>>>>
>>>> Cheers,
>>>> Ollie
>>>>
>>> --
>>> /**
>>>   * @author Oliver Gierke - Senior Software Engineer
>>>   *
>>>   * @param email ogierke at pivotal.io
>>>   * @param phone +49-151-50465477
>>>   * @param fax   +49-351-418898439
>>>   * @param skype einsdreizehn
>>>   * @see http://www.olivergierke.de
>>>   */
>>>
> --
> /**
>   * @author Oliver Gierke - Senior Software Engineer
>   *
>   * @param email ogierke at pivotal.io
>   * @param phone +49-151-50465477
>   * @param fax   +49-351-418898439
>   * @param skype einsdreizehn
>   * @see http://www.olivergierke.de
>   */
>